Energetic studies and developments are being made as to organic electroluminescent devices (organic EL devices), because highly luminescent emission is obtained from these devices with low-voltage driving. Generally, the organic EL devices are constituted of an organic layer including a light-emitting layer, and a pair of electrodes between which the organic layer is sandwiched. In such devices, electrons injected from the cathode are recombined with holes injected from the anode in the light-emitting layer, to produce excitons, whose energy is utilized to emit light.
Improvement in the efficiency of devices has been recently made by using a phosphorescence-emitting material. Iridium complexes, platinum complexes, and the like are such a phosphorescence-emitting material (see, for example, U.S. Pat. No. 6,303,238 and WO 00/57676). However, devices having both high efficiency and high durability have not been developed. There has been a need for development of phosphorescent materials capable of satisfying both.